Resistance welding apparatus having a fixed electrode and an electrode movable between a working position and two separate rest positions

Abstract

The invention relates to a resistance welding apparatus comprising a clamp (1) intended to support an arm comprising a first part (1A) supporting a fixed electrode (2) and a second part (1B) supporting a movable electrode (3) in translation, the electrodes (2, 3) being intended to be traversed by an electric current and to grip metal elements to weld them, the movable electrode (3) being configured to move between a working position (P0) in which the electrodes (2, 3) grip the metal elements to be welded and two opening positions allowing the metal elements to be welded to be inserted between the electrodes (2, 3) arranged opposite one another.

Description

Scope of the invention

[0001] The field of the invention is that of resistance welding devices.

[0002] The invention relates more particularly to such devices comprising a clamp intended to support an arm which consists of a first part supporting a fixed electrode and a second part supporting a mobile electrode in translation (see for example DE8815009, forming the basis of the preamble of claim 1). Prior art and its drawbacks

[0003] Resistance welding machines generate very strong electric currents that pass through electrodes via electrical contacts within each electrode. The electrodes are designed to grip materials, particularly metallic elements, in order to weld them, creating a weld point.

[0004] During the welding process, the passage of very high currents between the electrodes heats the materials due to their greater electrical resistance compared to the electrodes. For example, the very high currents passing through the electrodes range from 1,000 A to 15,000 Amperes.

[0005] Spot welding machines are known to have a unit with a clamp supporting an arm, for example, a C-shaped arm. The arm has two arms: one supporting a fixed electrode and the other supporting a moving electrode. Modern welding machines include an actuator, for example, a pneumatic cylinder. The use of such a pneumatic cylinder allows for the control and application of linear movement to the moving electrode. This linear movement allows, in one direction, the moving electrode to be brought closer to the fixed electrode in order to clamp the materials to be welded in a working position, with the clamp in a closed position. In the opposite direction, the moving electrode to be moved away from the fixed electrode in order to release the materials, with the clamp moving from a closed to an open position.

[0006] When the clamp is open, locking means secure the moving electrode in a rest position away from its working position.

[0007] Typically, the linear movement of the moving electrode from the rest position to the working position is initiated after activation of a control button configured to pressurize a chamber of the pneumatic cylinder.

[0008] Once the weld point has been made, the moving electrode is configured to move from the working position to the rest position after deactivation of the control button for example, so as to induce a vacuum in the chamber of the pneumatic cylinder which was then under overpressure.

[0009] One drawback of these resistance welding machines is that the distance between the working position and the resting position of the moving electrode is fixed. Specifically, this distance is predefined and optimized according to the geometries and thicknesses of the materials to be welded.

[0010] To overcome this drawback, resistance welding machines exist in which this distance can be increased by manually manipulating the moving electrode of the clamp to move it further away from the fixed electrode, i.e., by retracting the moving electrode. For example, means of locking the moving electrode in its resting position may include a clamping device, such as a clamping ring, against which the moving electrode is held and cannot move further away from the fixed electrode. In particular, the clamping device is designed, on the one hand, to be manually tightened onto the second part of the arm in order to hold the moving electrode in its resting position.On the other hand, following the manual loosening of the clamping means, it is possible to act directly on the moving electrode, and in particular to move it further away from the fixed electrode before manually tightening it to hold the moving electrode in a new resting position.

[0011] However, with such a clamping device, an operator must manually move the moving electrode to change its resting position. Furthermore, the clamping efficiency of such a device inevitably degrades over time, particularly with repeated tightening and loosening cycles. Objectives of the invention

[0012] The present invention proposes a welding apparatus equipped with a linear motion arm for a spot welding clamp with "C" movement.

[0013] The welding apparatus has a mechanism which allows, on the one hand, the moving electrode to be moved between the clamping position, i.e. the working position, and the rest position, and on the other hand, the moving electrode from the first rest position to a withdrawal position located at a distance from the working position greater than the distance separating the working position from the rest position.

[0014] Furthermore, the movement of the mobile electrode between its rest position and its retraction position is achieved without manual manipulation of the mobile electrode. Description of the invention

[0015] To this end, the invention relates to a resistance welding apparatus comprising a clamp for supporting an arm having a first part supporting a fixed electrode and a second part supporting a moving electrode, the electrodes being intended to carry an electric current and to grip metallic elements for welding, the moving electrode being configured to move between: a working position in which the electrodes grip the metal parts to be welded, a first opening position allowing the metal parts to be welded to be inserted between the electrodes arranged opposite each other, in which the moving electrode is in a first rest position and located at a first distance from the fixed electrode, a second opening position allowing the metal parts to be welded to be inserted between the electrodes arranged opposite each other, in which the moving electrode is in a second rest position and located at a second distance from the fixed electrode, greater than the first distance,

[0016] the welding apparatus comprising means for locking the moving electrode in the first rest position and actuating means intended to act on the locking means to allow the movement of the moving electrode towards the second rest position under the effect of return means.

[0017] The combined presence of locking, actuating, and return means allows for easy movement of the moving electrode from the first rest position to the second rest position. In particular, the return means ensure the automatic movement of the moving electrode from the first rest position to the second rest position without manual intervention on the moving electrode, but by pressing an actuating button configured to activate the actuating means.

[0018] Furthermore, allowing the clamp to open wider makes it possible to insert, between the two electrodes, metallic elements, for example automotive body panels, with thicknesses greater than the distance separating the working position of the moving electrode from its first rest position in which it is mechanically locked if no external force is applied to the actuation means.

[0019] Furthermore, when the metal elements to be welded include an obstacle, for example when the sheets for the manufacture of car bodies include a body element defined by a thickness greater than the distance separating the working position from the first rest position, it is thus possible to bypass it to carry out a weld at a precise point located on the other side of the obstacle.

[0020] Advantageously, the invention comprises the following features, taken alone or in combination: The resistance welding apparatus includes a jack rod on which the moving electrode is mounted to be driven in translation, the jack rod being integral with the return means configured to bring the moving electrode from the working position to the first rest position, and then to the second rest position when this movement is permitted; this makes it easy to move the moving electrode while having a simple mechanism to implement;This also allows for a single-acting cylinder which includes a single chamber capable of being, on the one hand, pressurized to move the electrode from the second rest position to the first rest position, and from the first rest position to the working position, and on the other hand, depressurized to, in combination with the return means, move the electrode from the working position to the first rest position, and from the first rest position to the second rest position; the locking means include a locking latch provided with a locking finger configured to cooperate with a stop formed on the outer surface of the cylinder rod;This allows for easy-to-implement locking means with the locking latch, which ensures the cylinder is blocked in translation from the first rest position to the second rest position when it cooperates with the stop; the locking latch is mounted to pivot around an axis of rotation between a locking position in which the locking finger cooperates with the stop and a release position in which movement of the moving electrode towards the second rest position is permitted; this allows for a simple-to-implement mechanism for enabling movement of the moving electrode; the actuation means include a release lever configured to actuate the pivoting of the locking latch; this allows manual switching between the locking and release positions. Brief description of the figures

[0021] Other features and advantages of the invention will now become apparent in greater detail in the following description of illustrative and non-limiting embodiments, with reference to the attached figures which represent: [ Fig.1 ] : there [ Fig.1 ] presents a schematic cross-sectional view of a clamp of a welding apparatus comprising a movable electrode according to an example embodiment, the movable electrode being in a first rest position; [ Fig. 2 ] : there [ Fig. 2 ] presents a schematic cross-sectional view of a clamp of a welding apparatus comprising a movable electrode according to an example embodiment, the movable electrode being in a working position; [ Fig.3 ] : there [ Fig.3] presents a schematic cross-sectional view of a clamp of a welding apparatus comprising a movable electrode according to an example embodiment, the movable electrode being in a second rest position; [ Fig. 4 ] : there [ Fig. 4 ] presents a schematic cross-sectional view centered on the means for locking the moving electrode of a clamp of a welding apparatus according to an exemplary embodiment, the locking means being in a position blocking the movement of the moving electrode from the first rest position to the second rest position; Fig. 5 ] : there [ Fig. 5 ] presents a schematic cross-sectional view centered on the means for locking the moving electrode of a clamp of a welding apparatus according to an exemplary embodiment, the locking means being in a position allowing the movement of the moving electrode from the first rest position to the second rest position; Fig. 6 ] : there [ Fig. 6] presents a front view of the moving electrode of a welding apparatus according to an exemplary embodiment, in which the locking means are in a position blocking the movement of the moving electrode from the first rest position to the second rest position; [ Fig. 7 ] : there [ Fig. 7 ] presents a front view of the moving electrode of a welding apparatus according to an example embodiment, in which the locking means are in a position allowing movement of the moving electrode between the first rest position and the second rest position. Detailed description

[0022] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0023] The invention relates to a resistance welding device for welding metallic elements together.

[0024] For example, the metal components can take the form of sheet metal intended for use in the manufacture of automobile bodies.

[0025] As illustrated in the figures 1 to 3 The welding apparatus includes a clamp 1. The clamp 1 has an arm comprising two parts located opposite each other. A first part 1A ends with a fixed electrode 2 and a second part 1B ends with a movable electrode 3.

[0026] Preferably, the arm and gripper assembly 1 is held by an operator or attached to the end of a robotic arm. The fixed electrode 2 and the moving electrode 3 are designed to carry an electric current to weld the metal parts clamped between the fixed electrode 2 and the moving electrode 3, creating a weld point. This electric current passes through the two electrodes 2 and 3 via, in particular, electrical contacts contained within each of them.

[0027] Preferably, the movable electrode 3 is mounted on a cylinder rod 4. The cylinder is, in one embodiment, a single-acting cylinder defined by a predefined stroke length.

[0028] Preferably, the cylinder rod 4 is inserted into a cylinder in which it slides. The cylinder rod 4 then carries the movable electrode 3 at one end and a piston sliding within the cylinder at its opposite end. The movement of the movable electrode 3 is then achieved by the forward and backward movements of the cylinder.

[0029] Preferably, a cylinder chamber is located on the sliding piston side. The forward and backward movements of the cylinder are then initiated by alternately pressurizing and depressurizing the cylinder chamber. For example, the pressurization of the cylinder chamber is generated by pressurizing a pneumatic fluid, such as compressed air, while the depressurization is achieved by removing a volume of compressed air from the cylinder chamber.

[0030] In this way, the mobile electrode 3 is driven in translation by the cylinder rod 4 in a first direction along a longitudinal axis X and in a second direction, opposite to the first direction along the longitudinal axis X. Thus, the cylinder rod 4, on the one hand, advances in the first direction, when the cylinder chamber is put under fluidic pressure, so that the mobile electrode 3 and the fixed electrode 2 grip the metal elements, and on the other hand, recoils in the second direction, when the cylinder chamber is put under fluidic pressure, to free the mobile electrode 3 from the metal elements and move it away from the fixed electrode 2 after possible completion of the weld point.

[0031] According to the invention, for the translational movement of the cylinder rod 4 in the second direction, the rod is attached to return means configured to disengage the movable electrode 3 from the metallic elements when the cylinder chamber is subjected to fluidic depressurization. In particular, the return means ensure the translational movement of the cylinder rod 4 in the second direction when the cylinder chamber is subjected to fluidic depressurization.

[0032] In one embodiment, the return means include a return spring 41 integral with the sliding piston. Preferably, the return spring 41 is a tension spring. In particular, the sliding piston is mounted on the return spring 41, which, when the return spring 41 is relaxed, exerts a restoring force on the cylinder rod 4 so that the rod moves in the second direction when the cylinder chamber is subjected to fluid vacuum.

[0033] Preferably, the translational drive of the cylinder rod 4 in the first direction is engaged when an operator continuously presses a control button to actuate the supply of compressed air to the cylinder chamber in order to put it under fluidic overpressure.

[0034] Preferably, the second-direction translation of the cylinder rod 4 is engaged when the operator releases the control button to create a fluid vacuum in the cylinder chamber. This allows the cylinder rod 4, under the effect of the return spring 41, to retract along the entire stroke length of the cylinder if this movement is permitted, i.e., if the cylinder rod is not blocked in any position in the meantime.

[0035] It should be noted that the assembly including the cylinder is designed to stabilize the position of the moving electrode 3 when the electrodes are either in contact with each other or in contact with the metal parts to be welded.

[0036] In [ Fig.1 Figure 1 shows the clamp open in a first open position. In particular, the moving electrode 3 is here in a first rest position P1, in which it is possible to insert the metal parts to be welded between the fixed electrode 2 and the moving electrode 3, which are then positioned opposite each other.

[0037] The mobile electrode 3 is then located at a first distance D1 from the fixed electrode 2.

[0038] The moving electrode 3 cannot move any further away from the fixed electrode 2. This movement is prevented by locking mechanisms that will be described later. Preferably, the initial distance D1 is less than the stroke length of the cylinder.

[0039] In [ Fig. 2 Figure 1 shows the clamp closed. The moving electrode 3 is in a working position P0, in which it is possible to perform the weld on the metal parts. The moving electrode 3 moves from the first rest position P1 to the working position P0 when the clamp 1 is closed, that is, when the cylinder chamber is pressurized to advance the cylinder rod 4. The moving electrode 3 then approaches the fixed electrode 2 to stabilize in the working position P0.

[0040] It should be noted that the moving electrode 3 also moves from the working position P0, represented in [ Fig. 2 ], towards the first rest position P1, represented in [ Fig.1 ], when the opening of the clamp 1 is engaged. In particular, during this movement, the rod 4 of the cylinder retracts until the locking means are engaged.

[0041] After acting on the locking means to unlock them, via actuation means which will be described later, the mobile electrode 3 moves from the first rest position P1 to a second rest position P2 represented in [ Fig.3 This movement is authorized by an operator when an over-opening of the clamp 1 is desired in order to open it further.

[0042] In particular, the [ Fig.3] represents the clamp 1 open according to the second opening position. In the second opening position, it is possible to insert, between the fixed electrode 2 and the moving electrode 3 arranged opposite each other, metal elements to be welded defined by a thickness greater than the metal elements that could be inserted through the clamp 1 when the moving electrode 3 was in the first rest position P1.

[0043] It should be noted that in the second opening position, the mobile electrode 3 is therefore located at a second distance D2 from the fixed electrode 2 which is greater than the first distance D1.

[0044] Thus, when the cylinder chamber is depressurized in order to retract the cylinder rod 4 under the effect of the return spring 41 attached to the sliding piston, the moving electrode 3 moves from the working position P0 to the first rest position P1, then to the second rest position P2 when this movement is allowed, that is to say when the cylinder rod 4 is not blocked by the blocking means.

[0045] THE Figures 4 and 5 represent, in particular, an example of the implementation of blocking methods. In particular, the [ Fig. 4 ] represents the means of locking in a locked position, that is to say in a blocked position, while the [ Fig. 5 ] represents the locking means in an unlocking position, i.e. in a release position of the cylinder rod 4.

[0046] In particular, the locking means here comprise a longitudinal groove 6 formed on the outer surface of the cylinder rod 4 and along its longitudinal axis X. Preferably, the longitudinal groove 6 is a keyway.

[0047] The locking means further include a locking latch 5 provided with a locking finger configured to fit into the longitudinal groove 6 and to make a sliding connection with it.

[0048] In particular, the groove 6 has a wall transverse to the longitudinal axis X forming a stop 61 in contact with a locking surface 51 of the locking finger. Preferably, the locking surface 51 of the locking finger is a flat surface.

[0049] Preferably, the locking latch 5 is integral with the actuation means described later. The actuation means are configured to lower the locking latch 5 so as to move from the locked position as illustrated in [ Fig. 4 ], towards the liberation position as illustrated in [ Fig. 5 ] when a force is exerted on them (the force being represented by an arrow in [ Fig. 5 ]).

[0050] In particular, the actuation means are configured to hold the locking latch 5 raised when not actuated, so that the locking finger is flush with a sliding surface of the groove 6 when the groove is opposite the locking finger. In this way, the stop 61 moves translationally along the longitudinal axis X while the locking finger remains in contact with the sliding surface of the groove 6 as the moving electrode 3 moves between the working position P0 and the first rest position P1. Thus, when the locking surface 51 of the locking finger is in contact with the stop 61, the movement of the moving electrode 3 from the first rest position P1 to the second rest position P2 is blocked.

[0051] To allow the movement of the cylinder rod 4 backwards in order to move the movable electrode 3 from the first rest position P1 to the second rest position P2, an operator exerts a force on the actuation means to lower the locking latch 5 in order to remove the locking finger from the groove 6. This prevents the locking surface 51 of the locking finger from contacting the stop 61.

[0052] According to one embodiment, the locking latch 5 is oblong in shape and therefore has two ends. Thus, to raise and lower it, its first end is mounted to pivot around an axis of rotation 9 formed by a pivot joint connecting the first end of the locking latch 5 and the second part of the arm.

[0053] The second end of the locking latch 5 is connected to the actuation means which, according to an example of an embodiment illustrated in Figures 6 and 7a slide 7, a release lever 10 preferably ending in a release finger 11, and a retaining spring configured to hold the locking latch 5 in the raised position when the release lever 10 is not actuated. It should be noted that the release finger 11 may be in the form of any type of actuation button.

[0054] Preferably, the slide 7 is oblong in shape and therefore has two ends. The slide 7 also has an opening through which the movable electrode 3 is inserted to allow its translational movement between the various positions mentioned above. One end of the slide 7 is connected to the second end of the locking latch 5, for example via a connecting element 8, which is either an integral part of the slide 7 or the locking latch 5, or a separate element. Here, the connecting element 8 is an extension of the first end of the slide that fits into the second end of the locking latch 5 to create a movable connection between the locking latch 5 and the slide 7.

[0055] According to one embodiment, the unlocking handle 10 comprises a rod having a first end and a second end, the ends being inclined relative to each other at an angle of inclination, for example, greater than 90°. Preferably, the first end of the rod is inserted into a second end of the slide 7, and the second end of the rod terminates in the unlocking finger 11. The rod is pivotally mounted about a pivot joint 12 made, preferably, at the angle of inclination, so as to set the slide 7 in motion.

[0056] The slide 7 is in particular configured to move in translation along a direction substantially transverse to the longitudinal axis X between the blocking position and the release position of the blocking means.

[0057] In particular, when the slider 7 is in a raised position as illustrated in figures 4 And 6The locking finger of the locking latch 5 is inserted into the groove 6. The movable electrode 3 is then locked in the first rest position P1. When the slide 7 is in a lowered position as illustrated in Figures 5 And 7The locking finger is withdrawn from the groove 6. In this position, part of the first end of the slide 7 and / or part of the second end of the latch 5, and possibly also the connecting element 8, are housed in a suitable recess 81 formed in the second part 1B of the gripper arm 1. The movable electrode 3 is then brought into the second rest position P2. The slide 7 moves from its raised position to its lowered position when, preferably, the operator manually releases the locking means by, for example, applying a force to the release finger 11. The slide 7 moves from its lowered position to its raised position by the application of a force by a return element. The slide 7 is held in its raised position by the force applied by the return element when no force is directly applied to the release finger 11.

[0058] In one embodiment, the release lever rod 10 is mounted on the retaining spring, which is preferably a compression spring. Thus, the pressure of the retaining spring, when compressed, exerts a force on the slide 7, naturally raising it and thus resisting its movement from its raised to its lowered position. This keeps the locking finger of the locking latch 5 in the groove 6, preventing the rearward movement of the cylinder rod 4 when no force is applied to the release finger 11.

[0059] Preferably, the release lever 10 is connected to the second part 1B of the gripper arm 1 by the pivot joint 12. Thus, the slide 7 moves from its raised position to its lowered position when the operator applies a rotational force to the release finger 11. For example, the rotational force that the operator must apply to the release finger 11 to unlock the locking means is a counterclockwise force. It should be noted that the release finger 11 then moves naturally, via the force exerted by the retaining spring, clockwise to return to its equilibrium position, i.e., its position when the slide 7 is in its raised position.

[0060] It should be noted that when the unlocking finger 11 is in its equilibrium position, the locking and actuation means are sufficiently rigid not to deform.

[0061] It is further indicated that the clamp 1 has a means of gripping and handling such as a handle 13, possibly removable, fixed to the second part 1B of the arm of the clamp 1.

[0062] The clamp 1 described above has the advantage of being able to open in two opening positions: an opening position corresponding to the first rest position P1 of the mobile electrode 3, and an over-opening position corresponding to the second rest position P2 of the mobile electrode 3.

[0063] This allows the clamp 1 to be adapted to metal thicknesses greater than the distance separating the electrodes 2, 3 in the first rest position P1, but also simplifies the positioning of the electrodes on either side of metal elements to be welded when access to these elements is reduced and difficult.

[0064] According to the invention, it is possible to carry out this over-opening without manually manipulating either of the electrodes or using a pneumatic circuit.

[0065] Although the present invention has been described with reference to the particular embodiments illustrated, it is not limited by these embodiments but only by the appended claims. It should be noted that changes or modifications may be made by those skilled in the art.

Claims

1. Resistance welding device comprising a clamp (1) to support an arm including a first part (1A) supporting a stationary electrode (2) and a second part (1B) supporting a translationally movable electrode (3), the electrodes (2, 3) being configured to be passed through by an electrical current and positioned to clamp metal elements in order to weld them, characterised in that the movable electrode (3) is configured to be movable between: a working position (P0) wherein the electrodes (2, 3) clamp the metal elements to be welded, a first opening position making it possible to insert, between the electrodes (2, 3) disposed opposite one another, the metal elements to be welded wherein the movable electrode (3) is in a first resting position (P1) and located at a first distance (D1) from the stationary electrode (2), a second opening position making it possible to insert, between the electrodes (2, 3) disposed opposite one another, the metal elements to be welded wherein the movable electrode (3) is in a second resting position and located at a second distance (D2) from the stationary electrode (2), greater than the first distance (D1) ; the welding device comprising blocking means which blocks the movable electrode (3) in the first resting position (P1), and actuating means which are designed to act on the blocking means to permit the movement of the movable electrode (3) to the second resting position (P2) under an effect of return means.

2. Resistance welding device according to claim 1, comprising a cylinder rod (4) whereon the movable electrode (3) to be translationally driven is mounted, the cylinder rod (4) being integral with the return means configured to return the movable electrode (3) from the working position (P0) to the first resting position (P1), then to the second resting position (P2) when the movement is permitted.

3. Resistance welding device according to claim 2, wherein the blocking means comprises a blocking latch (5) provided with a blocking finger configured to cooperate with a stop (61) arranged on an outer surface of the cylinder rod (4).

4. Resistance welding device according to claim 3, wherein the blocking latch (5) is mounted pivotable about an axis of rotation (9) between a blocking position wherein the blocking finger cooperates with the stop (61) and a release position wherein the movement of the movable electrode (3) to the second resting position (P2) is permitted.

5. Resistance welding device according to claim 4, wherein the actuating means includes an unlocking lever (10) configured to actuate pivoting of the blocking latch (5).

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